This invention relates, in general, to electrodes and more particularly to electrodes used for any frequency connections in plasma reactors.
Electrodes have been used for conducting any frequency or modulated voltages in reactors for quite some time. Generally, the electrodes that are constructed for this purpose are made of graphite material such as DFP-2POCO, or the like. Electrodes are generally used to conduct a modulated electrical voltage so that a plasma is generated in a reactor. The plasma is then used in the manufacture of semiconductor devices for either etching, deposition, or a combination of both. Graphite electrodes however have several disadvantages or problems such as material softness, brittleness, and a high incidence of breakage.
Graphite electrodes are generally, formed into a threaded shaft with a button or head on one end of the shaft. The screw threads are used to fasten the electrode into a semiconductor wafer susceptor or boat, while the button forms a contact point between the reactor and the boat. During cleaning of the boat the electrode is unscrewed from the boat and removed. Removal of the electrode from the boat prevents breaking or damaging of the electrode during the boat cleaning process. However, repeated assembly and disassembly of the electrode from the boat causes the screw threads to wear and to degrade with time. The degradation of the screw threads on the electrode causes contact problems which result in poor plasma uniformity, and in general poor reactor performance. Additionally, contamination of the semiconductor wafer or wafers can also be caused by poor contact problems. Generally, poor contact that results in arcing of a plasma, further results in particles or contamination being generated and deposited on the semiconductor wafer or wafers. The wearing of both the electrode threads and buttons are generally, attributed to the softness of the graphite material. The softness of the graphite material not only contributes to the aforesaid problems but, also causes an additional increase in maintenance time.
It can be seen that conventional graphite electrodes have severe limitations. Therefore, an electrode design that improves electrical contact, decreases maintenance time, decreases particle levels, and reduces cost would be highly desirable.